1. Field of the Invention
The present invention relates to a semiconductor element sealing material, and more particularly, to a semiconductor device using silicon carbide (SiC) or gallium nitride (GaN).
2. Background of the Related Art
In a semiconductor device using a silicon (Si) semiconductor element which has been generally used, sealing has been performed with epoxy resin or silicon gel to ensure insulation. SiC or GaN has better electrical characteristics than Si. Therefore, in recent years, research and development for putting the SiC or GaN semiconductor element to practical use have been conducted. The SiC or GaN semiconductor element is expected to replace the Si semiconductor element in the future. The SiC or GaN semiconductor element has better operation characteristics than the Si semiconductor element at a high temperature. In particular, SiC can operate up to 300° C.
When SiC is used in the semiconductor element, it is possible to increase the current density of the semiconductor element. However, when the current density of the semiconductor element increases, the amount of heat generated from the semiconductor element increases and the temperature of the semiconductor element increases. Therefore, it is necessary to increase the heat resistance performance of the sealing material used. When a general silicon gel according to the related art is used as the sealing material, in some cases, the silicon gel is degraded by oxidation at a high temperature of 175° C. or higher in an oxygen atmosphere and a crack occurs. In addition, when a general epoxy resin is used as the sealing material, in some cases, the resin is similarly degraded by oxidation and a crack occurs. Hereinafter, the degradation under the conditions of a high temperature and an oxygen atmosphere means thermal degradation in an oxygen atmosphere and is referred to as “thermal oxidation degradation”.
In the sealing of a semiconductor element, a technique has been known which doubly seals a semiconductor element with a first resin and a second resin in terms of humidity resistance (see JP 5-13623 A, Patent Document 1). In addition, in the manufacture of a power semiconductor module, a technique has been known which covers a semiconductor element with a first sealing material layer and a second sealing material layer in order to prevent the thermal fatigue of a solder layer adjacent to the semiconductor element (see JP 2010-219420 A, Patent Document 2).
However, in known techniques, it is difficult to maintain sealing characteristics at a high temperature of, for example, 175° C. or higher in the SiC or GaN semiconductor elements which operate at a high temperature.
In order to solve the above-mentioned problems, an object of the invention is to provide a semiconductor device that uses a SiC or GaN element, includes a sealing resin which is less likely to be degraded by thermal oxidation even when the semiconductor element operates at a high temperature of 175° C. or higher, can prevent the occurrence of a crack, and has high reliability and durability.